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UPSC Civil Service Exam Questions - Engineering

Q1:

A circle of radius 7 m has a standard error of 0.02 m on the radius. The standard error of its area is

A 0.04 m2

B 0.14 m2

C 0.28 m2

D 0.88 m2

ANS:C - 0.28 m2

A= πr^2.

dA/dr=2πr,
eA=er*dA/dr,
=. 0.02*2*r,
=. 0.02*2π*7,
=. 0.88 m^2.

So option D is correct.